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She said that people needed to change their behaviour to cope with the heat, with measures including allowing flexible working times so people can come in early when it is cooler or have a few hours off during the heat of the day.

She also said offices need to provide more water and allow workers to come in without ties or restrictive clothing.

"Climate change will mean that London will have temperatures more like Hong Kong in the future," she said.

"As this happens we need to adjust our behaviour patterns accordingly. Offices could look at flexible working arrangements, not being so tight about office clothing and having lots of water available."

Most who die in heatwaves are elderly. The 2003 August heatwave saw an 2,000 extra deaths in the UK - and 22,000 in Europe.

Already the UK is suffering from the recent heat as temperatures soared over the weekend.

London Ambulance Service reported a 30 per cent call-out increase due to a surge in people suffering chest pains, breathing difficulties and fainting.

The Scottish Ambulance Service said calls have been up 20 per cent for a week.

Prof Rydin also said communities need to be more aware of the vulnerable people who cannot cool down at night.

She said building stock needs to be improved so that the indoors cools down.

As part of climate change commitments, the Government are currently pushing a target to reduce emissions from building stock by 34 per cent reduction by 2020 and 80 per cent reduction by 2050 from 1990 levels. London has set itself an even more challenging target by requiring that existing emissions are reduced by 60 per cent by 2025 from the 1990 level. This means almost all the 3.2 million dwellings in London will need some modification.

However Prof Rydin warned that increasing efficiency must not mean that buildings become dangerously stuffy.

She explained that mould grows in buildings without adequate ventilation and this can harm the vulnerable, people with asthma and children.

"We have to be careful we are not insulating buildings does not have a negative effect on indoor air quality," she said.

More than 3.4 billion people - half the world's population - now live in cities.

The UCL (University College London)/Lancet Commission on Healthy Cities found that economic growth will not necessarily improve conditions.

Instead the report, that will be sent to governments around the world, concludes that all countries should be planning better to ensure cities are healthier places by building well ventilated energy efficient homes, providing public transport and cutting pollution.

Prof Rydin said improved urban planning could transform the lives of future generations.

“While cities have the potential to be healthier places for their citizens, this requires active planning."